Like https://docs.telerik.com/blazor-ui/components/combobox/custom-value and https://www.telerik.com/kendo-angular-ui/components/dropdowns/multiselect/custom-values/ so the user can input tags on their own without them being in the app data source.

---

ADMIN EDIT

The following sample may be useful in implementing this in the meantime: https://github.com/telerik/blazor-ui/tree/master/multiselect/add-new-item

---

I'm seeing a scroll bar appear then disappear as I type. Repeatedly typing "a" in the box will show/hide the scroll bar. Also typing "a" then backspace has the same behavior.

<TelerikMultiSelect Filterable="true" Data="@Countries"
                    @bind-Value="@Values"
                    Placeholder="Enter Balkan country, e.g., Bulgaria"
                    Width="350px" ClearButton="true"
                    AutoClose="false">
</TelerikMultiSelect>


@if (Values.Count > 0)
{
    <ul>
        @foreach (var item in Values)
        {
            <li>@item</li>
        }
    </ul>
}

@code {
    List<string> Countries { get; set; } = new List<string>();
    List<string> Values { get; set; } = new List<string>();   

    protected override void OnInitialized()
    {
        Countries.Add("Albania");
        Countries.Add("Bosnia & Herzegovina");
        Countries.Add("Bulgaria");
        Countries.Add("Croatia");      

        base.OnInitialized();
    }
}

---

ADMIN EDIT:

Currently, the component works the following way:

1. User starts typing in the input of the component.
2. Popup of the MultiSelect opens.
3. Skeleton is shown:
4. 
5.  Data processing starts.
6. After the data is processed, the skeleton is replaced with the actual data.

The scrollbar is shown by the skeleton and is always present (visible on step 3). The tricky part is that If the user is typing very fast, the Blazor framework bundles 2 renderings together and thus the scrollbar is not visible. The result is that the user sees a very brief flicker with the skeleton. Adding a small delay before showing the skeleton on step 3 will prevent the user from seeing the skeleton and thus remove the impression of seeing a "flicker".

As a workaround, you can hide the skeleton with CSS. This is applicable for all "select" components

<TelerikMultiSelect>
    <MultiSelectSettings>
        <MultiSelectPopupSettings Class="no-skeleton"></MultiSelectPopupSettings>
    </MultiSelectSettings>
</TelerikMultiSelect>

<TelerikComboBox>
    <ComboBoxSettings>
        <ComboBoxPopupSettings Class="no-skeleton"></ComboBoxPopupSettings>
    </ComboBoxSettings>
</TelerikComboBox>

<style>
    .no-skeleton .k-skeleton {
        display: none;
    }
</style>

---

Based on my testing and the online demos, each selection of an item in the dropdown for the Blazor MultiSelect closes the dropdown.

Is there a way to keep the dropdown open for the user to make multiple selections? The user could then click outside of the dropdown to close the dropdown.

The behavior I am describing is similar to the Kendo UI for jQuery MultiSelect "autoClose" configuration property.

https://docs.telerik.com/kendo-ui/api/javascript/ui/multiselect/configuration/autoclose

I would like to add a feature similar to the Tag Mode in the Kendo suite 

===========

ADMIN EDIT

===========

In the meantime, there are two possible workarounds:

1. Mimic the desired 'single' TagMode behavior and display the number of selected items inside the MultiSelect, instead of the selected items themselves.

This approach uses custom CSS, which hides the list of selected items and displays a dynamically updated count value. The most important bits are highlighted:

UI for Blazor 2.30

<TelerikMultiSelect Data="@Products" Class="single-tag-mode"
                    @bind-Value="@SelectedProductIDs"
                    ValueField="@nameof(Product.ProductID)"
                    TextField="@nameof(Product.ProductName)"
                    Placeholder="Select Products">
</TelerikMultiSelect>

<style>
    .single-tag-mode ul.k-reset {
        float: left;
    }

    .single-tag-mode ul.k-reset li.k-button {
        display: none;
    }

    .single-tag-mode ul.k-reset:before {
        content: "Selected items: @SelectedProductIDs.Count";
        display: inline-block;
        line-height: 1.8em;
        padding: 0 7px;
        vertical-align: bottom;
        border: 1px solid rgba(0, 0, 0, 0.08);
        background: #f5f5f5 linear-gradient(rgba(0, 0, 0, 0), rgba(0, 0, 0, 0.02));
    }
</style>

@code {
    List<Product> Products = new();
    List<int> SelectedProductIDs = new();

    protected override async Task OnInitializedAsync()
    {
        for (int i = 1; i <= 10; i++)
        {
            Products.Add(new Product()
            {
                ProductID = i,
                ProductName = "ProductName " + i
            });
        }

        await base.OnInitializedAsync();
    }

    public class Product
    {
        public int ProductID { get; set; }
        public string ProductName { get; set; }
    }
}

UI for Blazor 3.0

<TelerikMultiSelect Data="@Products" Class="single-tag-mode"
                    @bind-Value="@SelectedProductIDs"
                    ValueField="@nameof(Product.ProductID)"
                    TextField="@nameof(Product.ProductName)"
                    Placeholder="Select Products">
</TelerikMultiSelect>

<style>
    .single-tag-mode .k-input-values {
        float: left;
    }

    .single-tag-mode .k-input-values .k-chip {
        display: none;
    }

    .single-tag-mode .k-input-values:before {
        content: "Selected items: @SelectedProductIDs.Count";
        display: inline-block;
        line-height: 1.8em;
        padding: 0 7px;
        vertical-align: bottom;
        border: 1px solid rgba(0, 0, 0, 0.08);
        background: #f5f5f5 linear-gradient(rgba(0, 0, 0, 0), rgba(0, 0, 0, 0.02));
    }
</style>

@code {
    List<Product> Products = new();
    List<int> SelectedProductIDs = new();

    protected override async Task OnInitializedAsync()
    {
        for (int i = 1; i <= 10; i++)
        {
            Products.Add(new Product()
            {
                ProductID = i,
                ProductName = "ProductName " + i
            });
        }

        await base.OnInitializedAsync();
    }

    public class Product
    {
        public int ProductID { get; set; }
        public string ProductName { get; set; }
    }
}

2. Restrict the component's size and allow scrolling to see all selected items.

Use some custom CSS to set desired height of the container holding the selected items (.k-chip-list) and to control its overflow. You can use the Class parameter of the Multiselect to set your custom CSS class to the main wrapping container of the component and style a specific instance of the component, not all instances on the page/app.

In terms of controlling the container's height, you can:

• Set fixed height : the container will have fixed height and if its content exceeds it, a scrollbar will appear.
  
  
• Set max-height: when filled with content, the container will expand until it reaches its max height. Scrollbar will appear afterwards.
  

<style>
    .my-multiselect{
        overflow: auto;
        max-height: 60px;
    }
</style>

<TelerikMultiSelect Class="my-multiselect"
                    Data="@Countries"
                    @bind-Value="@Values"
                    Placeholder="Enter Balkan country, e.g., Bulgaria"
                    Width="350px" ClearButton="true" AutoClose="false">
</TelerikMultiSelect>

@code {
    List<string> Countries { get; set; } = new List<string>();
    List<string> Values { get; set; } = new List<string>();

    protected override void OnInitialized()
    {
        Countries.Add("Albania");
        Countries.Add("Bosnia & Herzegovina");
        Countries.Add("Bulgaria");
        Countries.Add("Croatia");
        Countries.Add("Kosovo");
        Countries.Add("North Macedonia");
        Countries.Add("Montenegro");
        Countries.Add("Serbia");
        Countries.Add("Slovenia");

        base.OnInitialized();
    }
}

In the MultiSelect Component you have Item, Footer, and Header Template sub components. I see no way of providing a template for the selected items. This would be a very nice feature to have. 

My specific use case it that I would like to add a tool tip to the selected tags. 

Thanks

I would like to have the ability to refresh the Multiselect Popup.

Currently, if the AutoClose="false" feature is applied and the items are programmatically selected, you cannot display them as selected while the Popup is opened. You need to close it first to accordingly update the selected items collection in it.

Hi,

I would like checkbox support including the check all checkbox on the multiselect component like: https://docs.telerik.com/devtools/aspnet-ajax/controls/combobox/functionality/checkbox-support

The url below shows how to create custom checkboxes in the multiselect component but adding a check all checkbox in the headertemplate does not update the multiselect popup

https://docs.telerik.com/blazor-ui/knowledge-base/multiselect-checkbox-in-dropdown?_ga=2.50111909.206897922.1631541466-694624900.1630583797&_gac=1.246637872.1631604077.EAIaIQobChMI8PnX6Pb98gIVkwCLCh381AjMEAAYASAAEgLROPD_BwE

At the moment, the OnChange even fires when:

• the user selects an item from the dropdown
• the user blurs the input
• the user presses enter in the input

The problem with the multiselect is that we have two extra actions:

• remove an already selected item from its own [x] button - OnChange does not fire even though the value changes
• clear all items with the ClearAll button - OnChange does not fire even though the value changes
• delete items with the backspace key

I have a requirement to be able to select multiple values. I have filtering enabled, but I only want the user to be able to select valid values and not enter custom data. My approach would be to clear any invalid data when the control loses focus. I want the MultiSelect input to be cleared when it looses focus (similar to the ComboBox behavior).

=========================

ADMIN EDIT

=========================

In the meantime, such behavior could be achieved with a JavaScript function called through the JS Interop.

@inject IJSRuntime JsInterop

<TelerikMultiSelect Filterable="true" Data="@Countries"
                    @bind-Value="@Values"
                    Placeholder="Enter Balkan country, e.g., Bulgaria"
                    Width="350px" ClearButton="true" 
                    AutoClose="false" OnBlur="@OnBlurHandler">
</TelerikMultiSelect>


@if (Values.Count > 0)
{
    <ul>
        @foreach (var item in Values)
        {
            <li>@item</li>
        }
    </ul>
}

@code {
    List<string> Countries { get; set; } = new List<string>();
    List<string> Values { get; set; } = new List<string>();

    async Task OnBlurHandler()
    {
        await JsInterop.InvokeVoidAsync("clearMultiselectInput");
    }

    protected override void OnInitialized()
    {
        Countries.Add("Albania");
        Countries.Add("Bosnia & Herzegovina");
        Countries.Add("Bulgaria");
        Countries.Add("Croatia");
        Countries.Add("Kosovo");
        Countries.Add("North Macedonia");
        Countries.Add("Montenegro");
        Countries.Add("Serbia");
        Countries.Add("Slovenia");

        base.OnInitialized();
    }
}

You can include the following script tag in your index page or place the function in a separate JavaScript file in your project. This function will clear all instances of the Multiselect inputs, so you don't have to specify separate selectors for each of them. If you only want to work with one instance, you can use another approach.

<script>
        function clearMultiselectInput() {
            var inputs = document.querySelectorAll(".k-multiselect .k-input-values input");
            inputs.forEach(e => e.value = "")                     
        }
</script>

Using row virtualization on MultiSelect, and am attempting to put a loading indicator into the popup content if the request to the server is still ongoing.

Problem with this is that the popup contents don't update if the popup is open when loading finishes.  I put together a reproduction on Telerik REPL showing the behavior I am experiencing.

https://blazorrepl.telerik.com/mvvQvVvN2458vinQ36

Note, Options finish loading (seen by the div update above the MultiSelect component), but if the popup is open, the contents do not update to reflect the loaded options.

My current workaround is to just make the MultiSelect disabled while it is doing its initial load.

I have a custom ICollection which I wanted to use with the MultiSelect control, however, the Value property is of type List<T>. This is very restrictive; the property should implement an interface for flexibility.

ADMIN EDIT: When voting, please add your comment on what you would prefer so we can gauge the needs people have and act accordingly.

To reproduce:

• Use the Local Data code snippet
• Open the popup
• Scroll down
• Close the popup
• Open the popup again
• Blank space will be rendered above the visible items.

Telerik Multi Select to have optional top level header item with check box & title "Select All" [Localizable]. 

If all items are selected, the display box of the Multi-Select should show "All Selected" instead of list of selected items.

Testing this Select All Checkbox sample in Safari produces a different result compared to other browsers.

Click on the CheckBox in the MultiSelect Header Template closes the popup in Safari. In other browsers (e.g. Chrome, Firefox) the popup remains open after checking the SelectAll CheckBox.